This invention relates to message storage systems generally and more particularly to a message storage system for storing messages as digitally encoded signals.
Various message storage services are well known in the prior art. For example, call answering equipment connected to a telephone customer's line intercepts incoming calls with a recorded announcement, records any message which a calling customer wishes to have delivered to the called customer, and, when instructed to do so, plays back any messages recorded for the called customer. Currently available message storage systems generally require equipment to be located on the customer's premises; however, centralized systems have been disclosed. For example, U.S. Pat. No. 3,141,931, issued to A. Zarouni on July 21, 1964, and assigned to the assignee of the present application, discloses centralized telephone answering equipment which is located within a central office. In that prior art arrangement, an announcement and record machine is assigned to each customer of the call answering service and the customer may record a personal announcement on his assigned machine. Any caller who directs a call to the customer when the service is activated hears the personal announcement and has an opportunity to record a message on the machine assigned to that customer. Subsequently, the customer may control the playback of the recorded messages by dialing an appropriate code. In a system with a large number of customers for such a service, the provision of a separate announcement machine for each customer becomes impractical.
U.S. Pat. No. 2,998,489, issued to R. R. Riesz on Aug. 29, 1961, and assigned to the assignee of the present application and U.S. Pat. No. 3,728,486, issued to C. R. Kraus on Apr. 17, 1973, disclose centralized message store and forward arrangements which work in cooperation with a telephone central office. In the systems disclosed in these prior art patents, a telephone customer who desires to have a recorded message delivered to a destination station dials a code to gain access to recording equipment in a store and forward system, dials the directory number of the destination station, and dictates a message. The systems record the dialed directory number and record the message in analog form on a magnetic tape recording device or the like. The systems are arranged to use the stored directory number to establish a connection over the telephone network to the destination station and to play the recorded message to the destination station. The prior art arrangements are adapted primarily for single message recording and do not offer solutions to the problems of a large scale centralized message storage system wherein storage facilities are shared by many customers and access must be provided on a real-time basis.
Centralized message storage systems recognize the advantages of removing the equipment from the customer's premises, e.g., the elimination of space requirements for the customer and the reduction of maintenance costs due to the elimination of remote maintenance trips. However, no centralized systems have been used extensively due to economic considerations and technological problems with the prior art configurations.